combined endarterectomy of the internal carotid artery and

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Persistent carotid hypoglossalartery is an unusual vascularanomaly that is reported in

less than 0.5% of routine cerebral an-giographies.1,2 It is one of the primi-tive carotid–basilar anastomosesthat, during embryogenesis, supplythe posterior cerebral circulation be-fore permeation of the circle of Willisand development of the vertebral ar-

teries. We describe a case of success-ful revascularization in an asympto-matic patient who had a stenotic,persistent hypoglossal artery associ-ated with an ipsilateral internalcarotid artery stenosis and a con-tralateral carotid artery occlusion.We discuss the operative findingsand surgical strategies and review theliterature briefly.

CASE REPORT

A 74-year-old healthy woman hada history of bilateral asymptomaticcarotid bruits. Duplex and continuousDoppler scanning demonstrated anocclusion of the left internal carotidartery and a critical stenosis (reductionof more than 80% of the surface area)of the left external carotid artery. On

Case ReportÉtude de cas

COMBINED ENDARTERECTOMY OF THE INTERNALCAROTID ARTERY AND PERSISTENT HYPOGLOSSAL ARTERY:AN UNUSUAL CASE OF CAROTID REVASCULARIZATION

Raymond Cartier, MD, FRCSC;* Paul Cartier, MD;† Gilles Hudon, MD, DABR;‡ Marc Rousseau, MD§

From the Montreal Heart Institute, Montreal, Que.

* Cardiovascular surgeon, Department of Cardiovascular Surgery, Montreal Heart Institute

†Vascular surgeon, Department of Cardiovascular Surgery, Hôtel-Dieu de Montréal

‡Vascular radiologist, Department of Radiology, Montreal Heart Institute

§Anesthesiologist, Department of Anesthesiology, Hôpital Jean Talon, Montreal

Accepted for publication Feb.15, 1995

Correspondence and reprint requests to: Dr. Raymond Cartier, Department of Surgery, Montreal Heart Institute, 5000 Belanger St., Montreal, QC H1T 1C8

Persistence of the hypoglossal artery is an unusual congenital abnormality of the carotid arterial system,and the simultaneous occurrence of atheromatous disease in the internal carotid artery and persistent hy-poglossal artery is even more uncommon. Carotid surgery in this situation is challenging, and the surgeonmust be aware of potential inherent pitfalls. A 74-year-old woman with asymptomatic stenosis of both in-ternal carotid and hypoglossal arteries associated with occlusion of the contralateral internal carotid arteryunderwent successful revascularization. The anatomy of this unusual lesion and the surgical strategies,which included cranial nerve dissection and mandibular subluxation, are reviewed.

La persistance de l’artère hypoglosse est une malformation congénitale inusitée du réseau carotidien, et laprésence simultanée de l’athéromatose de l’artère carotide interne et de la persistance de l’artère hypoglosseest encore plus rare. L’intervention chirurgicale sur la carotide dans cette situation pose un défi et lechirurgien doit être conscient des problèmes inhérents possibles. Une femme de 74 ans présentant unesténose asymptomatique à la fois de l’artère carotide interne et de l’artère hypoglosse liée à une occlusionde l’artère carotide interne contralatérale a subi une revascularisation réussie. L’article décrit l’anatomie decette lésion inusitée et les stratégies chirurgicales, qui comportaient une dissection du nerf crânien et unesubluxation mandibulaire.

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the right side, both internal and exter-nal carotid arteries were severelystenosed. The left vertebral artery wasperceived, but the right vertebralartery was not detected. The carotidangiogram confirmed the previousfindings but also disclosed an extracra-nial internal carotid artery branchstarting 4 cm above the carotid bifur-cation with a 60% (cross-diameter)proximal stenosis (Fig. 1). This sidebranch was further identified as a per-sistent hypoglossal artery. The rightvertebral artery was aplastic and theleft vertebral artery hypoplastic.Since the patient’s cerebral circula-

tion relied on a severely stenotic inter-nal carotid artery with poor collateralcirculation, we carried out an electiveprophylactic right internal carotid en-darterectomy.Surgery was performed with gen-

eral anesthesia. Systemic pressure was

pharmacologically maintained at150 mm Hg during the procedure,and a carotid shunt was inserted dur-ing the carotid cross-clamping period.The internal carotid stump and thecarotid gradient stenosis pressureswere measured at 40 and 70 mm Hgrespectively. The patient was he-parinized (5000 units), and thecarotid bifurcation was routinely ex-posed. However, in order to reach thehypoglossal artery surgical exposurehad to be extended. The descendenthypoglossal artery was divided and sowere the sternocleidomastoid vein andartery. The hypoglossal nerve was iso-lated and pulled down to allow bettervisualization. Then, the common va-gal and hypoglossal nerve sheath was

divided and the occipital branch of theexternal carotid artery was divided. Allthese steps combined with an unusualanterior subluxation of the lower jaw(by the assistant) allowed us to exposethe distal internal carotid artery andthe proximal hypoglossal artery.Endarterectomy of the common

carotid bifurcation was done first. Acalcified atherosclerotic plaque, reduc-ing both internal and external carotidartery lumens by at least 90%, wasfound extending, in a continuousmanner, up to the hypoglossal arterylumen. The endarterectomy was thenextended up to the proximal hy-poglossal artery. Before terminatingthe endarterectomy, the common andproximal internal carotid arteri-

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160 JCC, Vol. 39, no 2, avril 1996

FIG. 1. Right carotid angiogram. Internal carotid(IC) artery, external carotid (EC) artery and hy-poglossal artery (HA) are shown. Arrows indicatearea of stenosis.

FIG. 2. Right carotid angiogram from two different angles confirming patency of angioplasty. IC = in-ternal carotid artery, EC = external carotid artery, HA= hypoglossal artery.


otomies were closed with a saphenousvein patch angioplasty, and the shuntwas removed to allow better exposureof the hypoglossal endarterectomy.The hypoglossal endarterectomyended with a soft distal end point, andthe angioplasty was completed up tothe proximal hypoglossal artery.Carotid blood flow was re-establishedand carotid patency confirmed intra-operatively by continuous Doppler as-sessment. The surgical site was closedin a standard fashion. During removalof the shunt, the cerebral circulationwas interrupted for 10 minutes. Thepatient awoke with a transitory weak-ness of the left side, but this resolvedcompletely in less than 30 minutes.She left the hospital 4 days later withno central neurologic deficit. Postop-erative duplex scanning confirmed thepatency of the surgical site. Carotidangiography, performed 4 months af-ter the surgical procedure, showed awell-patent carotid and hypoglossal

angioplasty (Fig. 2). At 12-month fol-low-up, the patient was still asympto-matic with no neurologic sequelae.

DISCUSSION

Persistent extracranial divisions ofthe internal carotid artery were first re-ported in the 19th century, and theirembryologic origin was fully describedby Padget in 1948.3 Four primitivecarotid–basilar anastomoses areknown to be occasionally persistent:the trigeminal, the otic, the hy-poglossian and proatlantal arteries.The first three anastomoses normallyregress once the posterior communi-cating artery has joined the basilarartery formed by the fusion of bothposterior longitudinal neural arteries(Padget’s second stage). Further on,the basilar artery fuses with the verte-bral arteries issuing from transverseanastomoses of the 6th cervical seg-mental arteries. This is followed by the

regression of the proatlantal artery(Padget’s third stage).4 The persis-tence of the hypoglossal artery is thesecond most frequent of these anom-alies, occurring in less than 0.5% ofroutine cerebral angiographies and isnormally associated with hypoplasia oraplasia of vertebral and posterior com-municating arteries, as seen in the pre-sent case (Fig. 3).2 The artery nor-mally arises from the internal carotidartery at the level of the C1 to C3 ver-tebral bodies and then travels with the12th cranial nerve through the hy-poglossal canal and the posterior cra-nial fossa to join the basilar artery.5

Previous reports have cautionedsurgeons about the potential risk ofmajor cerebral ischemia during carotidcross-clamping, since the brain stem,cerebellum and ipsilateral cerebralhemisphere are vascularized by a sin-gle carotid artery.2,5 The present caseperfectly illustrates this situation.Considering the contralateral carotidocclusion and the absence of posteriorcommunicating arteries, the onlyresidual collateral network left wasthat supplied by a hypotrophic rightvertebral artery with no direct com-munication with the circle of Willis.Even though prophylactic carotidsurgery is still debated, it appears to usthat revascularizing the left carotidartery of this patient was imperative toavoid an eventual major cerebraldeficit. Although the transient hemi-paresis in the immediate postoperativeperiod could be attributed to an em-bolic phenomenon, it remains a con-cern that the critical dependence ofthe ipsilateral hemisphere during thetemporary flow interruption couldhave been related to it. Roederer andcolleagues6 have reported an annualcarotid artery occlusion rate of 46% inpatients with greater than 80% carotidstenosis. This patient was, then, ex-posed to a potential cerebrovascularaccident.

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FIG. 3. Right carotid and cerebral angiogram showing (left) internal carotid (IC) artery and hypoglos-sal artery (HA) joining basilar artery (BA) on vertical surface of pons. Arrow (right) points out absenceof posterior communicating artery.


Surgical revascularization in this casewas particularly difficult. The upwardextension of the carotid atheroma tothe hypoglossal artery demanded acarotid exposure to the limit of surgicalaccessibility. The internal carotid arteryis usually accessible in the first 4 cmabove the common carotid bifurcation.Lesions at the level of C2 or higher nor-mally require either a mandibular sub-luxation or division of the mandible andthe stylomandibular ligament to besafely accessible.7 Fortunately, by divid-ing the common hypoglossal–vagusjunction and ligating the occipitalbranch of the external carotid artery,along with a gentle manual mandibularsubluxation, we were able to achievesatisfactory exposure. In a recent review,Yamanaka and colleagues8 have com-piled over 134 cases of persistent hy-poglossal artery, of which 28 (20.9%)were associated with cerebrovasculardisease. To our knowledge, only onecase of isolated hypoglossal endarterec-tomy for symptomatic atheromatous

disease has been reported.9 However,the present case is the first report ofcombined internal carotid and hy-poglossal endarterectomy performedfor asymptomatic atheromatous disease.In conclusion, persistent hypoglos-

sal artery is an unusual feature, but itspreoperative recognition is essential inorder to minimize neurologic deficitsduring carotid surgery. The use of ashunt in this situation is strongly ad-visable, and the surgeon must be fa-miliar with high carotid exposure tohandle potential technical difficultiesencountered during the procedure.

References

1. Teal TS: Anomalous branches of theinternal carotid arteries. Radiology1972; 106: 567–573

2. Ouriel K, Green RM, DeWeese JA:Anomalous carotid–basilar anasto-moses in cerebrovascular surgery. JVasc Surg 1988; 7: 774–777

3. Padget DH: The development of the

cranial arteries in the human embryo.Contrib Embryol 1948; 32: 207–261

4. Hassen-Khodja R, Declemy S, BattM et al: Persistent hypoglossal artery.J Cardiovasc Surg (Torino) 1992; 33:199–201

5. McCartney SF, Ricci MA, LabrequeP et al: Persistent hypoglossal arteryencountered during carotid en-darterectomy. Ann Vasc Surg 1989;3: 257–260

6. Roederer GO, Langlois YE, Jager KAet al: The natural history of carotidarterial disease in asymptomatic pa-tients with cervical bruits. Stroke1984; 15: 605–613

7. Fisher DF, Clagett GP, Parker JI etal: Mandibular subluxation for highcarotid exposure. J Vasc Surg 1984;1: 727–733

8. Yamanaka K, Noguchi K, Hayasaki Ket al: Persistent primitive hypoglossalartery associated with arteriovenousmalformation. Neurol Med Chir1990; 30: 949–955

9. Osgood CP, Montanez JA,Karunaratne ER et al: Endarterectomyfor atheromatous hypoglossal artery. JNeurosurg 1983; 58: 935–936

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